Influence of Fe-F-co-doping on the dielectric properties of Ba0.6Sr0.4TiO3 thick-films

The influence of Fe acceptor and Fe-F acceptor-donor co-doping, oil the dielectric response of screen-printed Ba0.6Sr0.4TiO3; thick-films oil alumina Substrates has been investigated. The Ba0.6Sr0.4TiO3 powders were synthesized by freeze-drying, of sols. Permittivity, dielectric loss, and tunability were investigated Lit kHz frequencies with a planar capacitor structure, and at GHz frequences up to 40 GHZ using coplanar waveguide structures. Pure acceptor doping by Fe was found to have a distinct influence on permittivity and dielectric loss-factor Lit kHz-frequencies and at GHz frequencies due to an internal bias field and pairs of associated defects. Co-doping with F significantly suppresses the influence of the internal bias field and defect-associates at low and microwave frequencies. The commutation quality factor at 10 GHz and E-eff=5.8V mu m(-1) was increased by co-doping the thick-films with Fe and F. Such doped Ba0.6Sr0.4TiO3 films show a high potential for tunable microwave applications.